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| United States Patent |
5,022,306
|
|
Sayles
|
June 11, 1991
|
Method of ejecting an interceptor missile from its silo
Abstract
Disclosed is a method for ejecting an interceptor missile from the silo in
hich it is stored. The method employs an ultrahigh-burning rate (e.g.,
burning rate 10-20 inches per second) booster solid propellant grain in
combination with a fuse or a combination of fuses having a burning rate
(e.g. 25 to 100 inches per second) or a rate which is well above that of
the ultrahigh-burning rate booster solid propellant grain. The fuses are
designed to a predetermined exterior contour which is the same as the
exterior contour of the mandrel which would normally be used to provide
the contour to the internal perforation of the booster propellant grain.
The method include positioning the fuses longitudinally in the booster
motor instead of the normally used mandrel, and then casting the
propellant around the fuse or a combination of fuses and curing the
propellant to yield a booster solid propellant grain. When the fuses are
ignited by means of aft end ignition, their burning rapidly creates a port
in the center of the booster solid propellant grain. When the burning of
the fuses is near complete, and the propellant becomes exposed, the
booster propellant commences burning, and then provides the propulsive
power to boost the ballistic interceptor from its storage silo.
| Inventors:
|
Sayles; David C. (Huntsville, AL)
|
| Assignee:
|
The United States of America as represented by the Secretary of the Army (Washington, DC)
|
| Appl. No.:
|
779404 |
| Filed:
|
March 10, 1977 |
| Current U.S. Class: |
89/1.8; 60/256; 102/374; 102/380; 264/3.1 |
| Intern'l Class: |
F41F 003/04; F02K 009/00; F42B 015/10 |
| Field of Search: |
60/246
425/DIG. 12
86/1 R
264/3 R,3 C
89/1.8,1.813,1 A
102/49.7,103,70
|
References Cited
U.S. Patent Documents
| 3041914 | Jul., 1962 | Gurton et al. | 264/3.
|
| 3107620 | Oct., 1963 | O'Donnell | 102/289.
|
| 3137126 | Jun., 1964 | Madison | 60/256.
|
| 3267672 | Aug., 1966 | Craig et al. | 60/256.
|
| 3324795 | Jun., 1967 | Miles et al. | 102/289.
|
| 3570364 | Mar., 1971 | Thibodaux | 86/1.
|
| 3696749 | Oct., 1972 | Scanlon | 102/49.
|
| Foreign Patent Documents |
| 1257603 | Nov., 1946 | FR | 60/256.
|
Primary Examiner: Brown; David H.
Attorney, Agent or Firm: Bellamy; Werten F. W., Lane; Anthony T.
Claims
I claim:
1. A method of ejecting an interceptor missile from the silo in which it is
stored in a pre-launch mode, said method comprising:
(i) providing said interceptor missile with a solid propellant booster
motor comprised of an ultrahigh-burning rate booster solid propellant
grain encased in a booster motor case, said ultrahigh-burning rate booster
solid propellant grain containing an embedded fuse or a combination of
fuses of a metal-oxidant composition that has a burning rate range well
above that of said ultrahigh-burning rat booster solid propellant grain
said embedded fuse or a combination of fuses having a cylindrical
cross-section, and encased in a sheathing material comprised of a
composite, graphite filament-reinforced epoxy resin; said embedded fuse or
a combination of fuses designed to a predetermined exterior contour which
is the same as the exterior contour of the mandrel which would normally be
used to provide the contour to the internal perforation of the booster
solid propellant grain; said ultrahigh-burning rate booster solid
propellant grain formed by casting around said fuse or a combination of
fuses which are longitudinally positioned in said booster motor case, an
uncured booster propellant formulation and curing the propellant
formulation to yield said ultrahigh-burning rate booster solid propellant
grain;
(ii) positioning an ignition means for said embedded fuse or a combination
of fuses to provide for aft-end ignition;
(iii) igniting said embedded fuse or a combination of said fuses by aft-end
ignition to rapidly create by a burning process proceeding from the aft
end to forward end of said embedded fuse or a combination of fuses, an
internal perforation in the center of said ultrahigh-burning rate booster
solid propellant grain, said burning of said embedded fuse or a
combination of fuses proceeding at burning rate which is well in excess of
the ablation rate of said sheathing material of said fuse or a combination
of fuses to enable said sheathing material to be fully consumed during the
burning process to thereby expose a surface of said ultrahigh-burning rate
booster solid propellant grain at the time said burning process of said
fuse or a combination of fuses nears completion; and
(iv) allowing said exposed surface of said ultrahigh-burning rate booster
solid propellant grain to commence burning to thereby provide the
propulsive force to boost said ballistic interceptor missile from its
storage silo.
2. The method of claim 1 wherein said burning rate range of said embedded
fuse or a combination of fuses is about 25 to 100 inches per second and
wherein said fuse or a combination of fuses are designed to a
predetermined exterior contour of a cone.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application relates to my copending application Ser. No. 05,779,402,
filed Mar. 10, 1977, titled: "Method of Changing Propellant Grain
Configuration."
BACKGROUND OF THE INVENTION
Interceptor missiles are generally stored in an underground launch station
or silo which provides concealment, protection from the elements, and
protection from enemy attack. The underground launch station also provides
protection to inhabited areas nearby in the event of an accidental
in-launch station explosion. The missiles are part of a complex, remotely
controlled and operated system which includes a means for ejecting the
missile from the launch station. After the ejection of the missile, the
booster motor is ignited for providing thrust for the missile.
The contemporary method to eject an interceptor from its underground launch
station employs a large gas generator and a hydraulically-actuated piston
as the means to boost the interceptor from its station. As one could
surmise from the described means for ejection, the contemporary method
leads to complexities which increase the chances for failures in ejecting
the interceptor and directing it to the point of interception.
A preferred system for ejecting a missile from its storage silo would
obviate the need for hydraulic equipment and accessory items.
Therefore, an object of this invention is to provide a method for ejecting
a missile from its storage silo by a propulsive force derived from the
missile itself thereby obviating the need for hydraulic equipment and
accessory items.
Another object of this invention is to provide a booster solid propellant
grain having 100% loading with a portion of the loading being an embedded
ultrahigh-burning rate fuse or combination of fuses around which the
booster propellant is cast and cured. The fuse or combination of fuses is
designed to have an exterior contour which is the same as the exterior
contour of the mandrel which would normally be used for forming the
internal configuration or central perforation of the booster solid
propellant grain.
SUMMARY OF THE INVENTION
The method of this invention relates to ejecting an interceptor missile
from the silo in which it is stored in a pre-launch mode. The method
comprises:
1. Embedding a fuse or combination of fuses containing pyrotechnic
materials of ultrahigh-burning rates of the order of 25 to 100 inches per
second into the central perforation of the booster solid propellant grain.
The embedding is accomplished by first designing the fuse or combination
of fuses to an exterior contour which is the same as the exterior contour
of the mandrel which would normally be used to provide the contour to the
internal perforation of the booster solid propellant grain and then
casting the booster propellant formulation around the longitudinally
positioned fuse or a combination of fuses, curing the propellant, and
positioning the grain in the interceptor missile that is subsequently
positioned in a storage silo in a pre-launch mode.
2. Positioning an ignition means for the fuses to provide for aft end
ignition (e.g. ignition means of the electrically initiated type or other
type ignition means which can be initiated remotely are suitable).
3. Igniting the fuses by aft-end ignition to rapidly create a port or
internal perforation in the center of the booster solid propellant grain.
When the burning of the fuses is near complete as the propellant becomes
exposed at the aft end, the propellant commences burning, and then
provides the propulsive force to eject the interceptor missile from its
silo.
BRIEF DESCRIPTION OF THE DRAWING
The figures of the drawing depict configurations of an interceptor missile
at various stages during the using of the method of this invention.
FIG. 1 is a diagrammatic view showing a prefire motor configuration (before
fuse is ignited).
FIG. 2 is a diagrammatic view showing propellant grain configuration (when
fuse is partially consumed).
FIG. 3 is a diagrammatic view of the propellant grain configuration during
stabilized burning (after fuse is fully consumed).
DESCRIPTION OF THE PREFERRED EMBODIMENT
The method of this invention employs a fuse or a combination of fuses
having a burning rate well above that of the ultrahigh-burning rate
propellants which are being used in interceptor missiles. This means
burning rates of the order of 25 to 100 inches per second are required for
the fuse to perform satisfactorily in accordance with the method of this
invention.
An acceptable baseline fuse design for this application is a metaloxidant
composition having a cylindrical cross-section encased in a sheathing
material comprised of a composite, graphite filament-reinforced epoxy
resin. The pyrotechnic composition's burning rate needs to be well in
excess of the ablation rate of the sheathing material of the fuse, and the
sheathing material needs to be fully consumed during the burning process
so that the exhaust gases ar debris-free.
A suitable initiator for the fuse or a combination of fuses consists of a
Holex squib and an igniter charge of 1O g. of a stoichiometric
boron-potassium nitrate mixture which is inserted in a cavity at the aft
end of the fuse. It is bonded in with an adhesive, such as EPON 946 and
activator.
The characteristics and properties of the fuse required for use in this
invention have been described. The combination of the fuses and the
positioning of the fuses with respect to the propellant grain actually
determine the success of this invention. Therefore, it is necessary for
the fuse or combination of fuses to define the contour to the internal
perforation of the booster propellant since the fuse or combination of
fuses is used in place of the mandrel. A preferred design for the fuse or
a combination of fuses provide a cone-shaped exterior contour. Hence, the
fuses are first constructed of the described material to a predetermined
exterior contour as required by techniques employed in the art. The
constructed fuses are then positioned longitudinally in the booster motor
instead of (replacement of) the mandrel, and the booster propellant
formulation is cast around the fuses. After curing of the propellant to
the fuses and within the motor case, an integral booster solid propellant
grain results.
The booster motor is provided with the necessary accessory items required
for an interceptor missile; these accessor items would vary in accordance
with the sophistication required for the parameter of operation of the
interceptor missile system.
The interceptor missile is positioned in a storage silo from which it will
be ejected and subsequently directed to its point of interception. The
final step of the method of this invention proceeds by igniting the fuses
by means of aft-end ignition which is followed by rapid burning of the
fuse or combination of fuses to create a port in the center of the
booster's main propellant grain. When the burning of the fuses is nearly
complete, and the main propellant becomes exposed, the booster propellant
commences burning, and then provides the propulsive force to boost the
interceptor missile out of its silo. It is necessary to recognize that the
burning rate of the fuses proceeds at a fast rate with a generation of
considerably less exhaust gases than would be derived from the rocket
propellant. The exhaust gases would be of considerably higher molecular
weight and as a result, the propulsive power would be considerably less
than the exhaust gases derived from the burning main propellant.
Therefore, the rapid, ejective power for the interceptor missile is
derived from the propellant booster grain in itself as more clearly
explained in conjunction with the figures of the drawing.
FIG. 1 depicts booster motor 10 in a prefire motor configuration (before
fuse is ignited). The propellant grain 14 with the fuse 16 encased in
sheathing material 18, embedded therein as an integral unit, is encased in
a motor case 12. Not shown are ignition means and accessory items.
FIG. 2 depicts the booster motor and identities specified in FIG. 1
description in propellant grain configuration when the fuse is partially
consumed.
FIG. 3 depicts the booster motor and identities as specified in FIG. 2
description in a propellant grain configuration during stabilized burning
after the fuse is fully consumed.
The advantages that would accrue from this invention disclosure can be
enumerated as follows:
(a) It provides a mechanism for increasing the volumetric loading of
interceptor booster motors from 70% to 100%. The small percentage (about
8%) of the fuse loading performs the functions of rapidly creating the
internal perforation for the booster propellant grain while generating
considerably less exhaust gases having considerably higher molecular
weight that wouldn't be sufficient for ejection of interceptor missile;
however, it provides conservation of booster propellant grain by only
allowing ignition at time of fuse burn-out when propellant grain surface
is first exposed at aft end. This reaction time is extremely short (from
ignition of fuses to booster propellant grain ignition) because of high
burning rate of fuses.
(b) It provides additional time before it is necessary to commit the
interceptor to destroy an incoming target, or provides more time for the
replacement in the event that the interceptor which is launched first
fails to function satisfactorily.
(c) It provides a mechanism for reducing the action time, and this is
equivalent to a large increase in burn-out velocity.
(d) And, especially for low-commit systems, and for relatively short action
times, the launch delay time would be shortened, which is most significant
since launch delay time takes up a considerable portion and large
percentage of the action time.
The adoption of the method of fabricating a solid-propelled interceptor
motor used in the method of this invention offers several advantages as
additionally described below.
(1) Because of the high acceleration forces which would act on the
propellant grain in an unpressurized second-stage motor during booster
operation, the use of complicated, internal grain configurations, such as,
star points, etc., would be impractical because these would undergo
bending or shear off. By adopting the concept described in this invention,
the propellants configuration would be reinforced by this
fast-deflagrating mandrel, and as a consequence, configuration of any
intricacy could be used.
(2) The fast-deflagrating mandrel material would increase the thrust
derived from the motor, and serve to increase the motor loading efficiency
and mass fraction.
(3) This would also eliminate the need for a structural support tube which
would be inserted into the grain perforation to reinforce the propellant
grain so that it would be able to withstand the acceleration loads that it
would be subjected to during booster operation.
(4) The combustion of the mandrel would result in the generation of a large
exhaust efflux, and a rapid buildup of pressure to its operating pressure.
This would translate to a shortened action time which is essential for
low-commit interceptors to intercept at lower altitudes.
(5) This would make practical the use of the conventional two-stage
propulsion subsystem as well as a single-stage propulsion subsystem for
advanced interceptors. The single propulsive stage design has been
determined to be very sensitive insofar as mass fraction is concerned,
because of this limitation, the single-stage design was assessed as being
incapable of imparting the required velocity to an advanced interceptor.
(6) The propellant grain for the second-stage will have a conical
perforation in the aft end which blends into a rather large stress-relief
groove in the forward end. To fabricate such a configuration, a mandrel of
complex design will be required whereas this will not be necessary using
the approach described in this disclosure.
The fuse or a combination of fuses employed in this invention can be
constructed of a ultrahigh-burning rate composition selected from the
group consisting of an ultrahigh-burning rate difluoroamino-based
propellant as defined under Example I as follows:
EXAMPLE I
______________________________________
INGREDIENT WEIGHT %
______________________________________
Ethyl Acrylate-Acrylic Acid
27.5
TVOPA* 3.6
ERL-4221** 1.4
Carboranylmethyl Propionate
4.0
HMS Graphite Linter (100 .mu.m)
2.0
Aluminum Powder 11.0
Aluminum Flake 1.0
Ammonium Perchlorate 50.0
Lecithin 0.1
______________________________________
*Tris 1,2,3 [bis(1,2difluoroamino)ethoxy]propane
**4,5Epoxycyclohexylmethyl 4',5'epoxycyclohexylcarboxylate,
a high burning rate thermite material as defined under Example II as
follows:
EXAMPLE II
______________________________________
a metal selected from zirconium, boron
40 parts
or aluminum
lead (IV) peroxide 60 parts,
______________________________________
a high burning rate thermite material as defined under Example III as
follows:
EXAMPLE III
______________________________________
a metal selected from zirconium, boron
331/3 parts
or aluminum
plumbus-plumbic oxide (Pb.sub.3 O.sub.4)
662/3 parts,
______________________________________
a preformed shaped material selected from beads, pellets, or agglomerates
of a formulation as defined under Example IV as follows:
EXAMPLE IV
______________________________________
INGREDIENT WEIGHT %
______________________________________
Ammonium Perchlorate 48.55
Metal Fuel 48.55
Carboxyl-Terminated Polybutadiene
2.34
Prepolymer (HC434)
DER-332* 0.16
ERLA-0510** 0.38
Chromium Octoate (5.5% Cr)
0.02
______________________________________
##STR1##
##STR2##
(Note: The preformed, shaped material is combined and bound together with
an added binder material comprised of about 3-6 weight percent
hydroxylterminated polybutadiene prepolymer that is crosslinked with abou
0.5-1.0 weight percent of a diisocyanate crosslinking agent and containin
from about 0.5 to about 2.0 weight percent of an added carboranyl burning
rate catalyst), and a high burning rate composition as defined under
Example V as follows:
EXAMPLE V
______________________________________
Cesium or ammonium salt
0.5 to 2 parts
of dodecahydrodecaborane
resinous binder and inert
98.0-99.5
materials
______________________________________
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